题目:A Printer numbered consecutively the pages of a book, beginning with 1 on the first page. In numbering the pages, he printed a total of 189 digits. How many pages are there in the book?
问题:看了中文翻译并听了管老师的讲解,我都没弄明白这个题目的解题思路。的别是对“a total of 189 digits”的处理。
题目:If n is a prime number greater than 3, what is the remainder when n的平方is divided by 12?
问题:当管老师解题时,他出了3个方程式,分别是:
1) n=3A+1, n的平方=9A(square)+6A+1
2) n=3A+2, n的平方=9A(square)+12A+4
3) n=2A+1, n的平方=4A(square)+4A+1
我不明白的点是:这3个方程式是怎么推到或者是一看到题目就这么设出来的?
57)If m is a positive odd integer between 2 and 30, then m is divisible by how many different positive prime numbers?
1)m is not divisible by 3.
2)m is not divisible by 5.
条件1 我理解的是 M 只能2到30之间,那么就有5,7,11,13,17,19,23,29,这么多个prime numbers.
条件2 我理解的是 M 可以是 3,7,9,11,13,17,19,21,23,27,29 这些,21可以被3和7除, 我判断条件1完全可以,条件2 我不太确定
解答:
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解答:
sysadmin老师
提问:
62)if d is the positive integer and f is the product of the first 30 positive integers what is the value of d?
(1) 10d is a factor of f.
(2) d > 6
这个题目说d 是一个正整数,f 是30!阶乘,d的值多少,
这个题应该怎么推理?